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[Openvpn-users] ICMP Checksum Error between connected sites

  • Subject: [Openvpn-users] ICMP Checksum Error between connected sites
  • From: "Andrew Hall" <andyjohnhall@xxxxxxxxx>
  • Date: Wed, 18 Jul 2007 15:14:41 +0100

Hi there.

I'm running an OpenVPN server in London, and have two site-to-site
connections from branch offices in Venice and Munich.

Recently, I began to use the "client-to-client" directive on the
server so the two branch offices can communicate with each other.

However, I have encountered an odd problem.

>From one branch office to another branch office I cannot ping certain
IP addresses. The addresses happen to be associated with Avaya VoIP

All other pings between the branch offices work fine.

Now here's the very odd bit...

>From machines on the London network, I can ping these addresses in the
branch offices - but not from the actual OpenVPN server itself.

And as the branch offices are communicating with each other via the
server in London, perhaps there is a connection here.

I don't understand how I can ping from machines in the London office
to machines in the branch office, but not if I do so from the OpenVPN
server itself - which is on the same LAN.

And if you attempt a traceroute, you just see "Icmp checksum error".

Can anyone think what on earth could be wrong here?

I have triple-checked my routing, and all looks fine.

Any thoughts would be most welcome!
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